RFC 6207

Internet Engineering Task Force (IETF) R. Denenberg, Ed.
Request for Comments: 6207 Library of Congress
Category: Informational April 2011
ISSN: 2070-1721
The Media Types application/mods+xml, application/mads+xml,
application/mets+xml, application/marcxml+xml, and application/sru+xml
Abstract
This document specifies media types for the following formats: MODS
(Metadata Object Description Schema), MADS (Metadata Authority
Description Schema), METS (Metadata Encoding and Transmission
Standard), MARCXML (MARC21 XML Schema), and the SRU (Search/Retrieve
via URL Response Format) protocol response XML schema. These are all
XML schemas providing representations of various forms of information
including metadata and search results.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are a candidate for any level of Internet
Standard; see Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6207.

1. Introduction
The Library of Congress, on behalf of and in collaboration with
various components of the metadata and information retrieval
community, has issued specifications that define formats for
representation of various forms of information including metadata and
search results. This memo provides information about the media types
associated with several of these formats, all of which are XML
schemas.
MODS: Metadata Object Description Schema. An XML schema for a
bibliographic element set that may be used for a variety of
purposes, and particularly for library applications.
MADS: Metadata Authority Description Schema. An XML schema for an
authority element set used to provide metadata about agents
(people, organizations), events, and terms (topics, geographics,
genres, etc.). It is a companion to MODS.
METS: Metadata Encoding and Transmission Standard. An XML schema for
encoding descriptive, administrative, and structural metadata
regarding objects within a digital library.
MARCXML: MARC21 XML Schema. An XML schema for the direct XML
representation of the MARC format (for which there already exists
a media type, application/marc; see [RFC2220]). By "direct XML
representation", we mean that it encodes the actual MARC data
within XML. (This is in contrast to MODS: MARC uses codes for its
element names; MODS represents the same information but uses
semantically meaningful names while MARCXML uses the MARC codes.)
SRU: Search/Retrieve via URL Response Format. An XML schema for the
SRU response. SRU is a protocol, and the media type sru+xml
pertains specifically to the default SRU response. The SRU
response may be supplied in any of a number of suitable schemas,
RSS, ATOM, for example, and the client identifies the desired
format in the request, hence the need for a media type. This
mechanism will be introduced in SRU 2.0; in previous versions
(that is, all versions to date; 2.0 is in development), all
responses are supplied in the existing default format, so no media
type was necessary. SRU 2.0 is being developed within the
Organization for the Advancement of Structured Information
Standards (OASIS).

2. Registration for mods+xml
MIME media type name: application
MIME subtype name: mods+xml
Required parameters: None
Optional parameters: (charset) This parameter has semantics
identical to the charset parameter of the "application/xml" media
type as specified in [RFC3023].
Encoding considerations: Identical to those of "application/xml" as
described in [RFC3023].
Security considerations: See Section 8 of RFC 6207.
Interoperability considerations: There are no known interoperability
issues.
Published specification: [MODS-SCHEMA], [MODS].
Applications which use this media type: Various MODS-conformant
toolkits use this media type.
Additional information:
Magic number(s): None
File extension(s): .mods
Macintosh file type code(s): TEXT
Person and email address to contact for further information:
Ray Denenberg <rden@loc.gov>
Intended usage: COMMON
Restrictions on usage: None
Author/Change controller: The MODS specification was developed by
the Library of Congress and is maintained by the Library of
Congress in conjunction with the MODS Editorial Committee, which
has change control over the specification.

3. Registration for mads+xml
MIME media type name: application
MIME subtype name: mads+xml
Required parameters: None
Optional parameters: (charset) This parameter has semantics
identical to the charset parameter of the "application/xml" media
type as specified in [RFC3023].
Encoding considerations: Identical to those of "application/xml" as
described in [RFC3023].
Security considerations: See Section 8 of RFC 6207.
Interoperability considerations: There are no known interoperability
issues.
Published specification: [MADS-SCHEMA], [MADS].
Applications which use this media type: Various MADS conformant
toolkits use this media type.
Additional information:
Magic number(s): None
File extension(s): .mads
Macintosh file type code(s): TEXT
Person and email address to contact for further information:
Ray Denenberg <rden@loc.gov>
Intended usage: COMMON
Restrictions on usage: None
Author/Change controller: The MADS specification was developed by
the Library of Congress and is maintained by the Library of
Congress in conjunction with the MODS Editorial Committee, which
has change control over the specification.

4. Registration for mets+xml
MIME media type name: application
MIME subtype name: mets+xml
Required parameters: None
Optional parameters: (charset) This parameter has semantics
identical to the charset parameter of the "application/xml" media
type as specified in [RFC3023].
Encoding considerations: Identical to those of "application/xml" as
described in [RFC3023].
Security considerations: See Section 8 of RFC 6207.
Interoperability considerations: There are no known interoperability
issues.
Published specification: [METS-SCHEMA], [METS].
Applications which use this media type: Various METS conformant
toolkits use this media type.
Additional information:
Magic number(s): None
File extension(s): .mets
Macintosh file type code(s): TEXT
Person and email address to contact for further information:
Ray Denenberg <rden@loc.gov>
Intended usage: COMMON
Restrictions on usage: None
Author/Change controller: The METS specification was developed by
the Library of Congress and is maintained by the Library of
Congress in conjunction with the METS Editorial Board as an
initiative of the Digital Library Federation.

6. Registration for sru+xml
MIME media type name: application
MIME subtype name: sru+xml
Required parameters: None
Optional parameters: (charset) This parameter has semantics
identical to the charset parameter of the "application/xml" media
type as specified in [RFC3023].
Encoding considerations: Identical to those of "application/xml" as
described in [RFC3023].
Security considerations: See Section 8 of RFC 6207.
Interoperability considerations: There are no known interoperability
issues.
Published specification: [SRU-SCHEMA], [SRU].
Applications which use this media type: Various SRU conformant
toolkits use this media type.
Additional information:
Magic number(s): None
File extension(s): .sru
Macintosh file type code(s): TEXT
Person and email address to contact for further information:
Ray Denenberg <rden@loc.gov>
Intended usage: COMMON
Restrictions on usage: None
Author/Change controller: The SRU specification for versions earlier
than 2.0 is maintained at the Library of Congress, in conjunction
with the SRU Editorial Board. Version 2.0 (for which the sru+xml
media type pertains) is being developed within OASIS.

7. IANA Considerations
IANA has registered the five media types described in Sections 2, 3,
4, 5, and 6 in the MIME media type registry (in the Standards Tree).
8. Security Considerations
An XML resource does not in itself compromise data security.
Applications that retrieve XML files over a network by means of
dereferencing a Uniform Resource Identifier [RFC3986] are advised to
properly interpret the data so as to prevent unintended access.
Hence, the security issues described in Section 7 of [RFC3986] apply.
Because the media types described in this document use the "+xml"
convention, they share the security considerations described in
Section 10 of [RFC3023].
In general, security issues related to the use of XML in IETF
protocols are discussed in Section 7 of [RFC3470] also apply. In the
following sections, we review some aspects that are important for
document-centric XML as applied to text encoding.
8.1. Harmful Content
Any application that retrieves the XML media types described in this
specification needs to be aware of risks connected with injection of
harmful scripts and executable XML (i.e., "active content" as
described in [RFC4288]). Although XML inclusion mechanisms and the
use of external entities can introduce vulnerabilities to various
forms of spoofing and also reveal aspects of a service in a way that
may compromise its security, such vulnerabilities are application
specific. In any case, MODS documents do not contain "active
content".
8.2. Authenticity and Confidentiality
Historical and bibliographical information can often be encoded in
MODS documents, and such information might even have legal force in
some jurisdictions. Digitization and encoding of such information
might require technologies for assuring authenticity, such as
cryptographic check sums and electronic signatures. Similarly,
historical documents might in part or in their entirety be
confidential. Such confidentiality might be required by law or by
the terms and conditions such as in the case of donated or deposited
text from private sources. A text archive might need content
filtering or cryptographic technologies to meet such requirements.